The present invention pertains to providing data services and more particularly to providing data, voice and dispatch services over code division multiple access 2000 (CDMA 2000) system.
Providing data services over CDMA 2000 requires that the voice bearer traffic be transmitted through radio link protocol (RLP). Radio link protocol provides for two types of channels, a FCH channel which is the only type of channel for providing voice services and a DCCH channel.
For the DCCH, full frames of data must be transmitted. That is, if less than a full frame of bits are to be transmitted, then the frame must filled (padded) with unneeded bits in order to send a full frame. For the DCCH channel, when there is no data to send, only power control information is sent at approximately 800 bits per second.
For the FCH, full, half, eighth (& possibly quarter) rate frames of data may be transmitted. That is, the frame rate is generally the lowest rate frame which is large enough to carry the payload. The rest of the frame is then filled (padded) with unneeded bits in order to send the frame rate selected. For the FCH channel, when there is no data to send, power control information and an eighth rate frame is sent. Thus, when the FCH has no bearer data to send, it sends more power (generates more interference and drains more battery if a MS is sending it) than a DCCH would. If no bearer data is to be sent, then a FCH channel requires about ⅛ the power of a full frame rate frame plus the power required to send the power control information. In contrast, the DCCH only needs to send the power required to send the power control information when there is no bearer traffic to send.
In many systems, the RF link from the system to the mobile user (forward link) become RF interference limited when the system link is loaded with symmetric traffic. Typically, about eighty percent (80%) of the bits sent in a data call are sent on the forward link. This tends to also result a forward link interference limited system. As a result the forward link tends to become interference limited. Since data traffic is a growing percentage of the total traffic in modern systems, the forward link is expected to continue to be the limiting link in the typical system. However, it is possible, that in some systems, the reverse (mobile to base station link) can become the limiting link.
Accordingly, it is highly desirable to provide a data transmission, voice and dispatch services over CDMA 2000 while adding a minimum of interference to the interference limited links; regardless of the type of service provided.